The majority of single copy DNA in most organisms is interspersed with repetitive sequences, which would seem to argue the importance of this phenomenon for genome functions of some sort. The overall objective of this project is the analysis of the relative rate of evolution of expressed, interspersed single copy DNA versus that of its adjacent repetitive sequence. The intention is the testing of a hypothesis concerning mechanisms of evolution in which alterations of patterns of age regulation are a major force in evolution. High criterion reassociation will be used to fractionate Rana species' DNA into interspersed elements (repetitive plus single copy) and noninterspersed repetitive DNA. The sequences in turn will be used in the analysis of the rate of evolution of interspersed single copy DNA and its adjacent repetitive sequences. Graham, Dale E. (1978) "The Isolation of High Molecular Weight DNA from Whole Organisms and Large Tissue Masses." Anal. Biochem. 85, 609. Braun, B. A., Schanke, K. S., and Graham, D.E. (1978) "Isolation of Discrete Repetitive Sequence Classes from Xenopus DNA by High Temperature Reassociation." Nucleic Acids Res., in press.